UE4 - Imported normals/tangent symmetry issues. This is still a thing?

AlecMoody

Hi Everyone,
My current client is using UE4 and I am seeing the same issues as UE3 with seams when using symmetry. Letting unreal calculate normals and tangents fixes it- but I was under the impression most people were using a mikkspace normal maps and importing normals. Solutions? Are other people still seeing this?

FinalDragon

Hey Alec,

Are you making sure that the mesh has its overlapping UV offset when the normals are being baked? The only other common issue I've had where I've had to fix normals in UE4 is making sure there's a smoothing group split where I have UV seams. xNormal bakes in Mikkspace usually works as long as I follow those two rules.

AlecMoody

The bakes are fine- I'll make an example mesh this weekend.

ceebee

I've had this issue as well. It happens in both UE4 and Substance Painter with Mikkt. I am fully aware and avoided most issues it would be like UVs overlapped or offset and all kinds of normal attempts. Still get symmetry seam on things mirrored on themselves. It's most obvious with a broad specular material, the shinier an object is the less its noticeable.

ceebee

https://forum.allegorithmic.com/index.php?topic=7917.msg38569#msg38569

I made a thread on Allegorithmic's site and they were stumped. I'm surprised more people haven't caught on to this issue yet.

Jrhoades

So I have been having an issue with UE4 all day and found the solution I do not know if this will fix yours guys issue I hope it does.  When you import the FBX (I only know that FBX has this option) under Mesh there is an arrow click it to expose more options one of them will be Normal Import Method make sure that is set to Import Normal by default it is set to Compute Normal. I hope this fixes your guys issue like it fixed mine.

beartraps

I dunno if you guys are still having this problem, but what worked for me was moving the mirrored UV's over into 0-1 space. I bake with my mirrored UV's in the opposite quadrant to avoid errors and noticed the seam when i imported with those UV's in separate quadrants. Moving all UV's into 0-1 space fixed it for me.

musashidan

@AlecMoody the idea of mikkt or a synced workflow is that you allow both the baker and the engine to compute the normals off the mikkt tangent space. So rather than export/import custom normals you don't. You let the baker/engine do it automatically. 

AlecMoody

musashidan said:

@AlecMoody the idea of mikkt or a synced workflow is that you allow both the baker and the engine to compute the normals off the mikkt tangent space. So rather than export/import custom normals you don't. You let the baker/engine do it automatically. 

That is not true when it comes to unreal 4 (or most game engines right now). The unreal mikkspace workflow expects to use mesh normals from the file and calculate tangent using mikkspace. FWIW, source engine, unity, and unreal 4 all expect to use mesh normals from the low poly model and then calculate tangents.

This thread is old, and got bumped recently. I haven't tested this issue in about 6 months but assuming the behavior hasn't changed, there is some issue specific to meshes with symmetry. A few people suggested the cause might be UVs outside of the 0-1 space. At some point I will test it and report back if it solved the issue.